1. Field of the Invention
The present invention relates to a solution for fabrication of electron-emitting devices which is used to form electron-emitting regions of the electron-emitting devices, and manufacture methods of electron-emitting devices, electron sources, and image-forming apparatus based on the use of the solution.
2. Related Background Art
There are hitherto known two types of electron-emitting devices; i.e., thermionic cathode devices and cold cathode devices. Cold cathode devices include the field emission type (hereinafter abbreviated to FE), the metal/insulating layer/metal type (hereinafter abbreviated to MIM), the surface conduction type, etc.
Examples of FE electron-emitting devices are described in, e.g., W. P. Dyke and W. W. Doran, xe2x80x9cField emissionxe2x80x9d, Advance in Electron Physics, 8, 89 (1956) and C. A. Spindt, xe2x80x9cPhysical properties of thin-film field emission cathodes with molybdenum conesxe2x80x9d, J. Appl. Phys., 47, 5248 (1976).
One example of MIM electron-emitting devices is described in, e.g., C. A. Mead, xe2x80x9cOperation of Tunnel-Emission Devicesxe2x80x9d, J. Appl. Phys., 32, 646 (1961).
One example of surface conduction electron-emitting devices is described in, e.g., M. I. Elinson, Radio Eng. Electron Phys., 10, 1290, (1965).
Surface conduction electron-emitting devices operate based on such a phenomenon that when a thin film of small area is formed on a base plate and a current is supplied to flow parallel to the film surface, electrons are emitted therefrom.
As to such surface conduction electron-emitting devices, there have been reported, for example, one using a thin film of SnO2 by Elinson cited above, one using an Au thin film [G. Dittmer: Thin Solid Films, 9, 317 (1972)], one using a thin film of In2O3/SnO2 [M. Hartwell and C. G. Fonstad: xe2x80x9cIEEE Trans. ED Conf.xe2x80x9d, 519 (1975)], and one using a carbon thin film [Hisashi Araki et. al.: Vacuum, Vol. 26, No. 1, 22 (1983)].
As a typical configuration of those surface conduction electron-emitting devices, FIG. 17 schematically shows the device configuration proposed by M. Hartwell, et. al. in the above-cited paper.
In FIG. 17, denoted by reference numeral 1 is a base plate. 2 is an electron-emitting region-forming thin film formed of a metal oxide thin film made by sputtering into an H-shaped pattern. An electron-emitting region 3 is formed by energization treatment called Forming (described later).
Denoted by 4 is an electron-emitting region-containing thin film. Incidentally, the device length L1 defined as shown is about 0.5 mm to 1 mm and the device width W is about 0.1 mm.
In those surface conduction electron-emitting devices, it has heretofore been customary that, before starting the emission of electrons, the thin film 2 is subjected to an energization treatment called Forming to form the electron-emitting region 3.
The term xe2x80x9cFormingxe2x80x9d means treatment of applying a voltage across the electron-emitting region-forming thin film 2 to locally destroy, deform or denature it to thereby form the electron-emitting region 3 which has been transformed into an electrically high-resistance state.
The electron-emitting region 3 may be formed as a gap or gaps produced in part of the electron-emitting region-forming thin film 2. In this case, electrons are emitted from the vicinity of the gap.
The electron-emitting region-forming thin film containing the electron-emitting region produced by the Forming will hereinafter be referred to as an electron-emitting region-containing thin film 4.
The surface conduction electron-emitting device after being subjected to the Forming treatment emits electrons from the electron-emitting region 3 when a voltage is applied to the electron-emitting region-containing thin film 4 such that a current flows through the device surface.
The electron-emitting region-forming thin film 2 is formed by coating and drying a solution of an organic metal compound, heating and calcining the coated film for removal of an organic compound by thermal decomposition, and then producing a metal or metal oxide thin film. The coated film of the organic metal compound tends to have a relatively large crystal structure so that crystal patterns and boundary lines of the crystal patterns produced during the coating still remain after the step of heating and calcining. This results in a problem of unevenness in the film thickness and the resistance value.
Of organic metal compounds, particularly amines or ammine complexes of metal carboxylates tend to much sublimate and their films are thinned during the step of heating and calcining due to sublimation. This raises a problem that electrical resistances of the thinned films are not uniform and, hence, characteristics of devices in a lot are not uniform. It is also desired that, in each device, a resistance value of the electron-emitting region-forming thin film 2 be even between opposed electrodes.
An object of the present invention is to provide an organic metal compound capable of solving the problem of unevenness in film thickness experienced in the prior art, and also to provide an electron-emitting region-forming thin film from which an electron-emitting region can be formed by the conventional energization treatment called Forming.
The present invention employs an organic metal compound which is not crystallized during a step of coating.
The organic metal compound is preferably not melted during a step of heating and calcining.
Also, the organic metal compound is preferably not sublimated during a step of heating and calcining.
According to one aspect of the present invention, there is provided a solution (for fabrication of electron-emitting devices) for forming electron-emitting regions of electron-emitting devices, wherein the solution contains a metal carboxylate expressed by the following general formula (I), an organic solvent and/or water;
(R(COO)k)mMxe2x80x83xe2x80x83(I)
where k=a numeral from 1 to 4, m=a numeral from 1 to 4, and R=CnX2n+1xe2x88x92k  R=CnX2n+2xe2x88x92k where X=a hydrogen or halogen (total number of hydrogen and halogen atoms is 2n+1) , n=integer from 0 to 30, and M=metal, provided that when n is 0, k is 1 or 2.
According to another aspect of the present invention, there is provided a manufacture method of electron-emitting devices each provided between electrodes with a conductive film including an electron-emitting region, wherein a process of forming the conductive film in which the electron-emitting region is to be formed includes a step of coating and calcining a solution which contains a metal carboxylate expressed by the following general formula (I), an organic solvent and/or water;
(R(COO)k)mMxe2x80x83xe2x80x83(I)
where k=a numeral from 1 to 4, m=a numeral from 1 to 4, and R=CnX2n+1xe2x88x92k  R=CnX2n+2xe2x88x92k where X=a hydrogen or halogen (total number of hydrogen and halogen atoms is 2n+1) , n=integer from 0 to 30, and M=metal, provided that when n is 0, k is 1 or 2.
According to further aspects of the present invention, there are provided electron-emitting devices produced by the above manufacture method, an electron source in which the electron-emitting devices in plural number are arrayed, an image-forming apparatus including the electron source, and a manufacture method of the image-forming apparatus.